This invention relates to a gas compression type refrigeration system for cooling and/or heating which utilizes the latent heat of the coolant, and more particularly to the control of the coolant flow rate in such a system.
FIG. 1 shows one example of a conventional refrigeration system. In FIG. 1, reference numeral 1 designates a compressor; 2, a condenser, 3, a pressure reducing pipe; and 4, an evaporator. These components are connected to form a closed refrigeration circuit in which coolant circulates.
In such a conventional refrigeration system, the temperature and pressure of the coolant gas are increased by the compressor 1 and the gas is then liquified by cooling in the condenser 2. The temperature and pressure of the coolant liquid are decreased by the pressure reducing pipe 3, and the coolant liquid thus treated is introduced into the evaporator 4. In the evaporator 4, the coolant liquid absorbs heat from the environment while evaporating into a gaseous phase, thereby performing refrigeration. Thereafter, the coolant gas is drawn into the compressor 1 and the cycle is repeated. In FIG. 1, the arrows indicate the flow of the coolant.
It is well known in the art that, in such a refrigeration system, the suitable coolant flow rate depends on the evaporation temperature, and the coolant flow rate should be increased as the evaporation temperature increases. However, the conventional refrigeration system as shown in FIG. 1 is disadvantageous in that the coolant flow rate cannot be sufficiently adjusted. Therefore, when the evaporation temperature is high, the coolant flow rate is insufficient. Accordingly, the degree of superheat of the coolant at the outlet of the evaporator becomes excessively large, and the temperature of the compressor is increased. In addition, when the evaporation temperature is low, the coolant flow rate becomes excessive and liquid may return to the compressor, i.e. coolant may not have sufficient time to fully evaporate before arriving at the compressor input.